GABAa receptors play a critical role in anxiety, sleep and the pathogenesis of many neurological disorders. Molecular cloning of gamma-aminobutyric A (GABA)a receptors has revealed a considerable heterogeneity of constituent subunits. Different GABAa receptor isoforms in cells transfected with specific combinations of subunits have unique rates of channel transition between distinct conformational states that determines a "molecular kinetic fingerprint" of GABA responses. Using mice with specific deletion of subunit genes we will prove that this molecular fingerprint set the time course of inhibitory synaptic currents (IPSCs) a crucial factor in determining the strength of the inhibitory synapse and a target of many commonly prescribed drugs. We focus on cerebellar granular and stellate neurons where a progressive developmental decrease in IPSCs duration parallels changes in GABAa receptor subunit expression. Supported by our preliminary finding that the deletion of the alpha1 subunit of GABAa receptor prevents developmental changes in IPSCs' kinetics, our hypothesis is that distinct GABAa receptor subtypes, anatomically restricted and developmentally regulated lead to the specific functional properties of inhibitory activity that underlie behavior and neurological disorders. The outcome of our study will allow linking the heterogeneity of molecular structures to the functional heterogeneity of inhibitory synapses. Whole-cell recordings of synaptic and extrasynaptic GABA currents in neurons of the mouse cerebellum in slices and primary neuronal cultures will be complementary to recordings of GABA-activated channel currents in outside-out patches excised from these neurons. The biophysical study of native GABA channel will be integrated by studying those recorded from cells transiently transfected with specific subunits of GABAa receptors and from transgenic mice missing specific subunits. The goal is to identify native subunit combinations and ultimately link these different receptor combinations to their particular role in GABA-mediated inhibition in cerebellar neurons.